Integrated optical module

ABSTRACT

Provided here are: a mounting section having a light-emitting element for emitting an optical signal; a mounting section arranged alongside the mounting section and having a light-emitting element for emitting an optical signal that is different in wavelength from the optical signal; and an optical multiplexer having a filter for transmitting therethrough only the wavelength of the optical signal, a mirror for reflecting the optical signal transmitted through the filter, and a filter arranged alongside the filter, for transmitting therethrough only the wavelength of the optical signal, and for reflecting the optical signal reflected by the mirror and multiplexing it with the transmitted optical signal; wherein the light-emitting element is mounted in the mounting section to be displaced toward the light-emitting element from a center in a width direction across an emission direction of the optical signal.

TECHNICAL FIELD

The present application relates to an integrated optical module.

BACKGROUND ART

In optical transmission systems, in order to cope with the recent rapidincrease in communication capacity, a wavelength-multiplex opticaltransmission method is widely employed in which optical signals aretransmitted or received in such a manner that plural wavelength signalsare put together in a single optical fiber. The integrated opticalmodule is used for this wavelength-multiplex optical transmissionmethod, and is provided with a plurality of light-emitting elements withdifferent wavelengths and an optical multiplexer for multiplexing pluraloptical signals emitted from the plurality of light-emitting elementsinto a single optical fiber, that are incorporated in a common package,and has a function of transmitting these signals while putting themtogether in the single optical fiber. For example, as represented by anoptical module of Patent Document 1, an optical signal is reflectedagain and again by means of a filter and a mirror, to thereby bemultiplexed with an optical signal in another lane, and then theseoptical signals are emitted from the optical multiplexer. The opticalsignals multiplexed and emitted by the optical multiplexer are convergedby a condenser lens into a single optical fiber, and are then emitted ina state transmittable to a fiber optic transmission network, from theintegrated optical module.

In order to attain a large-capacity optical transmission system, it isrequired that many integrated optical modules be mounted in atransmission device, so that a small-sized integrated optical module ishighly recommended to increase the mounting density. A size of anintegrated optical module depends heavily on a size of its holder thatis largest among the members incorporated in a package. Among sizes ofthe holder, the lengthwise size (a size in an optical-signal travelingdirection) is determined depending on the interval between thelight-emitting elements. This is because, at the time of multiplexingthe optical signals, although the optical signal travels while beingreflected between a filter and a mirror that are adhered to the holder,this optical signal has to be placed at a position same as that of theother optical signal in an adjacent lane, at the time of reaching afilter of the adjacent lane after being reflected by the mirror.Accordingly, when the interval between the light-emitting elementsbecomes large, it is required to increase the length of the holder sothat the optical signal may be re-positioned at the same position of theoptical signal in the adjacent lane. Meanwhile, in accordance with theenhanced performance and reduced power consumption of the integratedoptical module, not only the light-emitting element but also othercomponents such as a monitor, a capacitor, etc. have come to be mountedtogether on a mounting board for the light-emitting element. Thus, themounting board is enlarged and this causes increase of the intervalbetween the light-emitting elements.

CITATION LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-open No.    2018-72674 (Paragraph 0015; FIG. 4 )

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

Accordingly, the conventional integrated optical module has a problemthat, in accordance with the enhanced performance and reduced powerconsumption thereof that are associated with the recent rapid increasein communication capacity, the mounting board is enlarged thus causingincrease of the interval between the light-emitting elements, so thatthe optical multiplexer as well as the holder is enlarged and thus theintegrated optical module is also enlarged.

This application discloses a technique for solving the problem asdescribed above, and an object thereof is to provide a small-sizedintegrated optical module due to reduction in size of the opticalmultiplexer.

Means for Solving the Problems

An integrated optical module disclosed in this application ischaracterized by comprising: a first mounting section having a firstlight-emitting element for emitting from a first light-emitting spotthereof, a first optical signal; a second mounting section arrangedalongside the first mounting section and having a second light-emittingelement for emitting from a second light-emitting spot thereof, a secondoptical signal whose wavelength is different from that of the firstoptical signal; a first collimating lens for transforming the firstoptical signal emitted from the first light-emitting spot, into parallellight; a second collimating lens for transforming the second opticalsignal emitted from the second light-emitting spot, into parallel light;and an optical multiplex section having a first filter for transmittingtherethrough only the wavelength of the first optical signal transformedinto parallel light by the first collimating lens; a front-side mirrorfor reflecting the first optical signal transmitted through the firstfilter; and a second filter arranged alongside the first filter, fortransmitting therethrough only the wavelength of the second opticalsignal transformed into parallel light by the second collimating lens,and for reflecting the first optical signal reflected by the front-sidemirror and multiplexing it with the transmitted second optical signal;

wherein the first light-emitting element is mounted in the firstmounting section so as to be displaced from its center in a widthdirection across an emission direction of the first optical signal,toward the second light-emitting element; and the second light-emittingelement is mounted in the second mounting section so as to be displacedfrom its center in a width direction across an emission direction of thesecond optical signal, toward the first light-emitting element.

Effect of the Invention

According to this application, since the adjacent light-emittingelements are paired and mounted on their respective mounting boards soas to be closer to each other, it becomes possible to reduce the size ofthe optical multiplexer. Thus, it is also possible to achieve reductionin size of the integrated optical module in which the opticalmultiplexer is incorporated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an entire structure of an integratedoptical module according to Embodiment 1.

FIG. 2 is a plan view showing an internal configuration of theintegrated optical module according to Embodiment 1.

FIG. 3 is a plan view showing a configuration of mounting sections inthe integrated optical module according to Embodiment 1.

FIG. 4 is a plan view showing an internal configuration of aconventional integrated optical module.

FIG. 5 is a flowchart for illustrating operations of the integratedoptical module according to Embodiment 1.

FIG. 6 is a diagram for explaining a manufacturing method of mountingsections in the integrated optical module according to Embodiment 1.

FIG. 7 is a plan view showing another configuration of mounting sectionsin the integrated optical module according to Embodiment 1.

FIG. 8 is a plan view showing another configuration of mounting sectionsin the integrated optical module according to Embodiment 1.

FIG. 9 is a plan view showing a configuration of an optical multiplexerin an integrated optical module according to Embodiment 2.

FIG. 10 is a plan view showing a configuration of an optical multiplexerin an integrated optical module according to Embodiment 3.

MODES FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a schematic view showing an entire structure of an integratedoptical module 101 according to Embodiment 1. FIG. 2 is a plan viewshowing an internal configuration of the integrated optical module 101.FIG. 3 is a plan view showing a configuration of mounting sections inthe integrated optical module 101.

As shown in FIG. 1 , the integrated optical module 101 according toEmbodiment 1 is configured with: each mounting section 2 i in which alight-emitting element 1 i for converting an electric signal into anoptical signal 3 i is installed; each collimating lens 4 i fortransforming the optical signal 3 i emitted from the light-emittingelement 1 i into parallel light; an optical multiplexer 5 formultiplexing each optical signal 3 i; a package 6 in which the foregoingcomponents are accommodated; an optical fiber 8; and a condenser lens 7for converging emitted light from the optical multiplexer into theoptical fiber 8. Note that the suffix i represents each number thatindicates a lane number (channel number) in the integrated opticalmodule, and is given as 0, 1, 2 or 3 in this embodiment (i=0, 1, 2, 3).

As shown in FIG. 2 , the optical multiplexer 5 is configured with: eachfilter 9 i for transmitting therethrough an optical signal 3 i having awavelength corresponding to the lane i and reflecting optical signalshaving wavelengths other than that wavelength; a mirror 10 located on aside opposite to the filter 9 i, as a front-side mirror for reflectingoptical signals having any wavelengths; a mirror 19 located on thefilter 9 i-side and between the filter 9 ₁ and the filter 92, as aback-side mirror; and a holder 11 having two parallel surfaces on whichthe filter 9 i and the mirrors 10, 19 are fixed. The mirrors 10, 19 areeach formed in such a manner that a dielectric multi-layer film isvapor-deposited on a glass substrate.

As shown in FIG. 3 , the mounting section 2 i has: a light-emitting spot13 i of the light-emitting element 1 i at which the optical signal 3 icorresponding to an electric signal 12 i emerges; a monitor PD(Photodiode) 14 i for monitoring an emitted light amount of thelight-emitting element 1 i; a terminal resistor 15 i for applying avoltage to a modulator of the light-emitting element 1 i in response tothe electric signal 12 i; an AC (Alternating Current) coupling capacitor16 i for preventing a DC (Direct Current) component in the electricsignal 12 i from flowing to the terminal resistor 15 i to thereby causeconsumption of power; and gold wires 17 for electrically connectingelectrodes of the light-emitting element and the monitor PD withelectrodes on the mounting board.

With respect to the mounting section 2 i, a pair of the mounting section2 ₃ as a first mounting section and the mounting section 2 ₂ as a secondmounting section, and a pair of the mounting section 2 ₁ as a thirdmounting section and the mounting section 2 ₀ as a fourth mountingsection, constitute a light-emitting-element pair 18 b as a firstlight-emitting-element pair and a light-emitting-element pair 18 a as asecond light-emitting-element pair, respectively. Thelight-emitting-element pair 18 a is a pair of the light-emitting element1 ₀ and the light-emitting element 1 ₁ that are adjacent to each other,in which the light-emitting element 1 ₀ is mounted on a mounting board22 ₀ so as to be displaced from its center toward the light-emittingelement 1 ₁, and the light-emitting element 1 ₁ is mounted on a mountingboard 22 ₁ so as to be displaced from its center toward thelight-emitting element 1 ₀, so that the pair of the adjacentlight-emitting elements are mounted on their respective mounting boardsso as to be closer to each other. Likewise, the light-emitting-elementpair 18 b is a pair of the light-emitting element 1 ₂ and thelight-emitting element 1 ₃ that are adjacent to each other, in which thelight-emitting element 1 ₂ is mounted on a mounting board 22 ₂ so as tobe displaced from its center toward the light-emitting element 1 ₃, andthe light-emitting element 1 ₃ is mounted on a mounting board 22 ₃ so asto be displaced from its center toward the light-emitting element 1 ₂,so that the pair of the adjacent light-emitting elements are mounted ontheir respective mounting boards so as to be closer to each other.

In FIG. 4 , a plan view is shown which represents the internalconfiguration of a conventional integrated optical module. In FIG. 4 ,for comparison's sake, the size of a mounting section 2 i is the same asthat in the case of Embodiment 1. In Embodiment 1, the light-emittingelement 1 i in each of the light-emitting-element pairs 18 a and 18 b ismounted so that the light-emitting spot 13 i of the light-emittingelement 1 i is positioned to be displaced from the center of aconventional mounting board 22 i in its width direction across the lightemission direction, toward the adjacent light-emitting element in thatlight-emitting-element pair, to the extent of one fourth of the width.In this case, as shown in FIG. 2 , when the distance between thelight-emitting spots 13 ₃, 13 ₂ of the respective light-emittingelements 1 ₃, 1 ₂ in the light-emitting-element pair 18 b is assumed tobe d1, the distance between the light-emitting spots 13 ₁, 13 ₂ of thenearby light-emitting element 1 ₁ and light-emitting element 1 ₂ in thelight-emitting-element pair 18 a and the light-emitting-element pair 18b, is given as 3 d 1. Accordingly, the distance between thelight-emitting spots 13 ₀, 13 ₃ of the light-emitting element 1 ₀ andthe light-emitting element 13 at both ends of the set of thelight-emitting-element pair 18 a and the light-emitting-element pair 18b, is given as 5 d 1. In contrast, in the conventional case, as shown inFIG. 4 , the distances between the respective light-emitting spots 13 iof the light-emitting elements 1 i are each given as 2 d 1, and thus thedistance between the light-emitting spots 13 ₀, 13 ₃ of thelight-emitting element 1 ₀ and the light-emitting element 1 ₃ in themounting section 2 ₀ and the mounting section 2 ₃ at both ends, is givenas 6 d 1.

Next, description will be made about operations of the integratedoptical module 101 according to Embodiment 1. FIG. 5 is a flowchart forillustrating the operations of the integrated optical module 101.

First of all, the optical signal 3 ₃ emitted from the light-emittingelement 1 ₃ enters into the optical multiplexer 5 after beingtransformed into parallel light by the collimating lens 4 ₃ and is thentransmitted through the filter 9 ₃, and thereafter, it is reflected bythe mirror 10 to reach the filter 9 ₂ (Step S501).

Further, the optical signal 3 ₂ emitted from the light-emitting element1 ₂ enters into the optical multiplexer 5 after being transformed intoparallel light by the collimating lens 4 ₂ and is then transmittedthrough the filter 9 ₂, and thereafter, it is multiplexed with theoptical signal 3 ₃ (Step S502). Here, the length of the holder 11 in theoptical-signal propagation direction is designed so that the position ofthe optical signal 3 ₃ having been reflected by the mirror coincideswith the position of the optical signal 3 ₂ having been transmittedthrough the filter 9 ₂.

Then, the multiplexed optical signals 3 ₃, 3 ₂ are reflected again andagain by the mirror 10 and the mirror 19, to reach the filter 9 ₁ (StepS503).

Further, the optical signal 3 ₁ emitted from the light-emitting element1 ₁ enters into the optical multiplexer 5 after being transformed intoparallel light by the collimating lens 4 ₁ and is then transmittedthrough the filter 9 ₁, and thereafter, it is multiplexed with theoptical signals 3 ₃, 3 ₂ (Step S504). Here, when the distance betweenthe light-emitting spots 13 ₃, 13 ₂ of the respective light-emittingelements 1 ₃, 1 ₂ in the light-emitting-element pair 18 b is assumed tobe d1, the distance between the light-emitting spots 13 ₁, 13 ₂ of thenearby light-emitting element 1 ₁ and light-emitting element 1 ₂ in thelight-emitting-element pair 18 a and the light-emitting-element pair 18b, is given as 3 d 1, so that a position at which the optical signals 3₃, 3 ₂ from the light-emitting elements 1 ₃ 1 ₂ in thelight-emitting-element pair 18 b reach the filter 9 ₁ (a reflectionposition) coincides with a position at which the optical signal 3 ₁ fromthe light-emitting element 1 ₁ that constitutes the otherlight-emitting-element pair 18 a is transmitted through the filter 9 ₁.

Then, the multiplexed optical signals 3 ₃, 3 ₂, 3 ₁ are reflected by themirror 10, to reach the filter 9 ₀ (Step S505).

Further, the optical signal 3 u emitted from the light-emitting element1 ₀ enters into the optical multiplexer 5 after being transformed intoparallel light by the collimating lens 4 ₀ and is then transmittedthrough the filter 9 ₀, and thereafter, it is multiplexed with theoptical signals 3 ₃, 3 ₂, 3 ₁ (Step S506). Here, the distance betweenthe light-emitting element 1 ₀ and the light-emitting element 1 ₀ thatconstitute the light-emitting-element pair 18 a is also given as d1.Thus, a position at which the optical signals 3 ₃, 3 ₂ from thelight-emitting elements 1 ₃, 1 ₂ in the light-emitting-element pair 18b, as well as the optical signal 3 ₁ from the light-emitting element 1 ₁in the light-emitting-element pair 18 a, reach the filter 9 ₁ (areflection position) coincides with a position at which the opticalsignal 3 ₀ is transmitted therethrough from the light-emitting spot 13 ₀in the light-emitting element 1 ₀ that constitutes the otherlight-emitting-element pair 18 a.

Lastly, the multiplexed optical signals 3 ₃, 3 ₂, 3 ₁, 3 ₀ are emittedfrom the optical multiplexer 5 (Step S507). The optical signals emittedfrom the optical multiplexer 5 are converged by the condenser lens 7into the single optical fiber 8, and are then emitted in a statetransmittable to a fiber optic transmission network, from the integratedoptical module.

As described previously, in order that the optical signals 3 i aremultiplexed, one optical signal is required to get a position thatcoincides with the position of each of the nearby optical signals, whilebeing reflected again and again by the mirrors 10, 19 and the filter 9i, so that a length of the holder 1 ₁ of the optical multiplexer 5 inthe incident direction of the optical signal is given proportionally toa distance between the optical signals.

Accordingly, in Embodiment 1, the distance between the light-emittingspots of the respective adjacent light-emitting elements is d1, which ishalf the distance 2 d 1 of the conventional integrated optical module,so that it is possible to reduce to half the length of the holder 1 ₁ inthe incident direction of the optical signal. Further, with respect alsoto a width of the holder 1 ₁ in the transverse direction across theincident direction of the optical signal, in Embodiment 1, the widthfrom the light-emitting spot 13 ₀ to the light-emitting spot 13 ₃ is 5 d1 even though it is 6 d 1 in the conventional case, so that it ispossible to reduce the size of the optical multiplexer in terms of thatwidth as well.

It is noted that, in Embodiment 1, for the light-emitting-element pair18 a and the light-emitting-element pair 18 b, two types of mountingboards are required, one of which corresponds to the mounting boards 22₀, 22 ₂ on which the light-emitting elements are each formed on the leftside viewed from the emission direction of the optical signal, and theother of which corresponds to the mounting boards 22 ₁, 22 ₃ on whichthe light-emitting elements are each formed on the right side viewedfrom the emission direction of the optical signal. In this regard, inEmbodiment 1, a mounting board 22 shown in FIG. 6 may be used. FIG. 6(a)is a top view (front surface), FIG. 6(b) shows a side surface, and FIG.6(c) is a bottom view (back surface). As shown in FIG. 6 , on the frontsurface and the back surface of the mounting board 22, terminalresistors 15R, 15L, light-emitting-element installation regions 20R,20L, capacitor installation regions 21R, 21L and monitor PD installationregions 22R, 22L, are respectively formed at positions that may besymmetrical about an emission direction of the optical signal.

When the mounting board 22 is to be used as the mounting board 22 ₀ (22₂), the back side thereof is utilized and thus the light-emittingelement 1 ₀ (1 ₂) is installed in the light-emitting-elementinstallation region 20L, the capacitor 16 ₁ (16 ₂) is installed in thecapacitor installation region 21L, and the monitor PD 14 ₀ (14 ₂) isinstalled in the monitor PD installation region 22L. Further, when themounting board 22 is to be used as the mounting board 22 ₁ (22 ₃), thefront side thereof is utilized and thus the light-emitting element 1 ₁(1 ₃) is installed in the light-emitting-element installation region20R, the capacitor 16 ₁ (16 ₃) is installed in the capacitorinstallation region 21R, and the monitor PD 14 ₁ (14 ₃) is installed inthe monitor PD installation region 22R.

Accordingly, using the mounting boards 22 of one type, it is possible toconstitute the pair so that the light-emitting elements are locatedcloser to each other. This makes it possible to achieve reduction insize of the optical multiplexer and reduction in size of the integratedoptical module. In addition, since the mounting boards of thelight-emitting elements constituting a pair can be of the same type, itis possible to reduce the types of members, to thereby increase thenumber of the mounting boards per one type. This makes it possible toreduce the manufacturing cost of the mounting board and thus to achievecost reduction.

FIG. 7 is a plan view showing another configuration of the mountingsections in the integrated optical module 101 according to Embodiment 1.As shown in FIG. 7 , in the light-emitting-element pair 18 a of theintegrated optical module 101, the light-emitting spot 13 ₀ isimplemented in the light-emitting element 1 ₀ so as to be displaced fromits center in a width direction across the emission direction of theoptical signal 3 ₀, toward the light-emitting spot 13 ₁; and thelight-emitting spot 13 ₁ is implemented in the light-emitting element 1₁ so as to be displaced from its center in a width direction across theemission direction of the optical signal 3 ₁, toward the light-emittingspot 13 ₀. Likewise, in the light-emitting-element pair 18 b, thelight-emitting spot 13 ₂ is implemented in the light-emitting element 1₂ so as to be displaced from its center in a width direction across theemission direction of the optical signal 3 ₂, toward the light-emittingspot 13 ₃; and the light-emitting spot 13 ₃ is implemented in thelight-emitting element 1 ₃ so as to be displaced from its center in awidth direction across the emission direction of the optical signal 3 ₃,toward the light-emitting spot 13 ₂.

Accordingly, a distance between the light-emitting spot 13 ₀ and thelight-emitting spot 13 ₁ of the light-emitting element 1 ₀ and thelight-emitting element 1 ₁ that constitute the light-emitting-elementpair 18 a, as well as a distance between the light-emitting spot 13 ₂and the light-emitting spot 13 ₃ of the light-emitting element 1 ₂ andthe light-emitting element 1 ₃ that constitute thelight-emitting-element pair 18 b, is given as d2, provided that d2<d1,so that it is possible to further reduce the size of the opticalmultiplexer.

FIG. 8 is also a plan view showing another configuration of the mountingsections in the integrated optical module 101 according to Embodiment 1.As shown in FIG. 8 , a mounting board 22 a is formed on which: a singlelight-emitting element 1 a with integrated two light-emitting spots 13₀, 13 ₁, serving as the light-emitting-element pair 18 a of theintegrated optical module 101, for emitting optical signals withdifferent wavelengths; the monitor PDs 14 ₀, 14 ₁; and the capacitors 16₀, 16 ₁; are installed. Likewise, a mounting board 22 b is formed onwhich: a single light-emitting element 1 b with integrated twolight-emitting spots 13 ₂, 13 ₃, serving as the light-emitting-elementpair 18 b, for emitting optical signals with different wavelengths; themonitor PDs 14 ₂, 14 ₃; and the capacitors 16 ₂, 16 ₃; are installed.

Accordingly, a distance between the light-emitting spot 13 ₀ and thelight-emitting spot 13 ₁ of the light-emitting element 1 a thatconstitutes the light-emitting-element pair 18 a, as well as a distancebetween the light-emitting spot 13 ₂ and the light-emitting spot 13 ₃ ofthe light-emitting element 1 b that constitutes thelight-emitting-element pair 18 b, is given as d3, provided thatd3<d2<d1, so that it is possible to still further reduce the size of theoptical multiplexer.

As described above, the integrated optical module 101 according toEmbodiment 1 comprises: the mounting section 2 ₃ having thelight-emitting element 1 ₃ for emitting from the light-emitting spot 13₃, the optical signal 3 ₃; the mounting section 2 ₂ arranged alongsidethe mounting section 2 ₃ and having the light-emitting element 1 ₂ foremitting from the light-emitting spot 13 ₂, the optical signal 3 ₂ whosewavelength is different from that of the optical signal 3 ₃; thecollimating lens 4 ₃ for transforming the optical signal 3 ₃ emittedfrom the light-emitting spot 13 ₃, into parallel light; the collimatinglens 4 ₂ for transforming the optical signal 3 ₂ emitted from thelight-emitting spot 13 ₂, into parallel light; and the opticalmultiplexer 5 having the filter 9 ₃ for transmitting therethrough onlythe wavelength of the optical signal 3 ₃ transformed into parallel lightby the collimating lens 4 ₃; the mirror 1 ₀ for reflecting the opticalsignal 3 ₃ transmitted through the filter 9 ₃, and the filter 9 ₂arranged alongside the filter 9 ₃, for transmitting therethrough onlythe wavelength of the optical signal 3 ₂ transformed into parallel lightby the collimating lens 4 ₂, and for reflecting the optical signal 3 ₃reflected by the mirror 1 ₀ and multiplexing it with the transmittedoptical signal 3 ₂;

wherein the light-emitting element 1 ₃ is mounted in the mountingsection 2 ₃ so as to be displaced from its center in a width directionacross the emission direction of the optical signal 3 ₃, toward thelight-emitting element 1 ₂; and the light-emitting element 1 ₂ ismounted in the mounting section 2 ₂ so as to be displaced from itscenter in a width direction across the emission direction of the opticalsignal 3 ₂, toward the light-emitting element 1 ₃.

Thus, the adjacent light-emitting elements are paired and mounted ontheir respective mounting boards so as to be closer to each other, sothat it is possible to reduce the interval between the light-emittingelements constituting a pair.

In another aspect, the integrated optical module further comprises: themounting section 2 ₁ and the mounting section 2 ₀ which are formed asthe light-emitting-element pair 18 a in a manner corresponding to thelight-emitting-element pair 18 b formed of the mounting section 2 ₃ andthe mounting section 2 ₂, and which are arranged alongside each other inthis order on an opposite side of the mounting section 2 ₂ relative tothe mounting section 2 ₃; the collimating lens 4 ₁ for transforming theoptical signal 3 ₁ emitted from the light-emitting spot 13 ₁ in themounting section 2 ₁, into parallel light; the collimating lens 4 ₀ fortransforming the optical signal 3 ₀ emitted from the light-emitting spot13 ₀ in the mounting section 2 ₀, into parallel light; the filter 9 ₁and the filter 9 ₀ which are matched to the wavelengths of the opticalsignal 3 ₁ and the optical signal 3 ₀ from the light-emitting-elementpair 18 a, respectively, and which are arranged alongside each other inthe optical multiplexer 5 in a manner corresponding to the filter 9 ₃and the filter 9 ₂; and the back-side mirror 19 for reflecting betweenthe filter 9 ₂ and the filter 9 ₁, a multiplexed wave of the opticalsignal 3 ₃ and the optical signal 3 ₂;

wherein, assuming that a distance between the light-emitting spot 13 ₃in the mounting section 2 ₃ and the light-emitting spot 13 ₂ in themounting section 22 is d1, a distance between the light-emitting spot 13₂ in the mounting section 22 and the light-emitting spot 13 ₁ in themounting section 2 ₁ is nd1 (n denotes an integer of 2 or more).

Thus, since the length of the holder in the optical multiplexer is givenproportionally to the distance between the optical signals, when theadjacent light-emitting elements are paired and mounted on theirrespective mounting boards so as to be closer to each other, it becomespossible to reduce the size of the optical multiplexer. Thus, it is alsopossible to achieve reduction in size of the integrated optical modulein which the optical multiplexer is incorporated.

In another aspect, the light-emitting spot 13 ₃ is implemented in thelight-emitting element 1 ₃ so as to be displaced from its center in awidth direction across the emission direction of the optical signal 3 ₂,toward the light-emitting spot 13 ₂, and the light-emitting spot 13 ₂ isimplemented in the light-emitting element 1 ₂ so as to be displaced fromits center in a width direction across the emission direction of theoptical signal 3 ₂, toward the light-emitting spot 13 ₃. Thus, thedistance between the light-emitting spots can be made shorter, so thatit is possible to achieve further reduction in size of the opticalmultiplexer and thus in size of the integrated optical module.

In another aspect, the mounting section 2 ₃ and the mounting section 2 ₂are integrated with each other so that the light-emitting spot 13 ₃ andthe light-emitting spot 13 ₂ are implemented side by side. Thus, thedistance between the light-emitting spots can be made much shorter, sothat it is possible to achieve further reduction in size of the opticalmultiplexer and thus in size of the integrated optical module.

In another aspect, the mounting section 2 ₃ and the mounting section 2 ₂are each formed of a mounting board, on both surfaces of which aninstallation region for the light-emitting element 1 ₃ and aninstallation region for the light-emitting element 1 ₂ are respectivelyprovided. Thus, since the mounting boards of the light-emitting elementsconstituting the light-emitting element pair can be of the same type, itis possible to reduce the types of members, to thereby increase thenumber of the mounting boards per one type. This makes it possible toreduce the manufacturing cost of the mounting board and thus to achievecost reduction.

Embodiment 2

In Embodiment 1, a glass substrate on which a dielectric multi-layerfilm is vapor-deposited is used as each of the mirrors 10, 19, whereasin Embodiment 2, description will be made about a case where thedielectric multi-layer film is vapor-deposited on the holder.

FIG. 9 is a plan view showing a configuration of an optical multiplexerin an integrated optical module according to Embodiment 2. As shown inFIG. 9 , in the integrated optical module according to Embodiment 2, themirror 10 and the mirror 19 are each formed in such a manner that thedielectric multi-layer film is vapor-deposited directly on theglass-made holder 11 instead of the glass substrate used in Embodiment 1on which the dielectric multi-layer film is to be vapor-deposited. Theother configuration of the integrated optical module accordingEmbodiment 2 is similar to that of the integrated optical module 101 ofEmbodiment 1, so that reference numerals that are the same as those inFIG. 2 are given to the corresponding parts and description thereof isomitted here.

As described above, in the integrated optical module according toEmbodiment 2, the glass-made holder 11 provided with the dielectricmulti-layer films that are vapor-deposited directly on that holder inits locations where the mirrors are to be fixed, is used. This makes itpossible not only to achieve an effect described in Embodiment 1, butalso to eliminate a step of mounting the mirror and to reduce the numberof components of the optical multiplexer, because of the mirrorformation directly on the holder. Thus, it is possible to achieve costreduction.

Embodiment 3

In Embodiment 1, a glass substrate on which a dielectric multi-layerfilm is vapor-deposited is used as the mirror 19, whereas in Embodiment3, description will be made about a case where a large-sized filter isinstead used.

FIG. 10 is a plan view showing a configuration of an optical multiplexerin an integrated optical module according to Embodiment 3. As shown inFIG. 10 , in the integrated optical module according to Embodiment 3,such a filter 9 ₁ is formed whose size is expanded so as to cover thelocation of the holder 11 where the mirror 19 is to be fixed inEmbodiment 1, and which serves also as the mirror 19. Note that a filter9 ₂ like this may be used instead of the filter 9 ₁. The otherconfiguration of the integrated optical module according Embodiment 3 issimilar to that of the integrated optical module 101 of Embodiment 1, sothat reference numerals that are the same as those in FIG. 2 are givento the corresponding parts and description thereof is omitted here.

As described above, in the integrated optical module according toEmbodiment 3, the mirror 19 is established in such a manner that thefilter 9 ₁ or the filter 9 ₂ covers the holder 11 up to the locationthereof where the mirror 19 is to be fixed, to thereby cause reflection.This makes it possible not only to achieve an effect described inEmbodiment 1, but also to eliminate a step of mounting the mirror and toreduce the number of components of the optical multiplexer. Thus, it ispossible to achieve cost reduction.

In this application, a variety of exemplary embodiments and examples aredescribed; however, every characteristic, configuration or function thatis described in one or more embodiments, is not limited to being appliedto a specific embodiment, and may be applied singularly or in any ofvarious combinations thereof to another embodiment. Accordingly, aninfinite number of modified examples that are not exemplified here aresupposed within the technical scope disclosed in the presentdescription. For example, such cases shall be included where at leastone configuration element is modified; where at least one configurationelement is added or omitted; and furthermore, where at least oneconfiguration element is extracted and combined with a configurationelement of another embodiment.

DESCRIPTION OF REFERENCE NUMERALS AND SIGNS

1 i (1 ₁, 1 ₂, 1 ₃, 1 ₄): light-emitting element, 2 i (2 ₁, 2 ₂, 2 ₃, 2₄): mounting section, 3 i (3 ₁, 3 ₂, 3 ₃, 3 ₄): optical signal, 4 i (4₁, 4 ₂, 4 ₃, 4 ₄): collimating lens, 9 i (9 ₁, 9 ₂, 9 ₃, 9 ₄): filter,10: mirror, 11: holder, 13 i (13 ₁, 13 ₂, 13 ₃, 13 ₄): light-emittingspot, 22 i (22 ₁, 22 ₂, 22 ₃, 22 ₄): mounting board, 101: integratedoptical module.

1.-7. (canceled)
 8. An integrated optical module, comprising: a firstlight-emitting-element pair which is formed of a first mounting sectionhaving a first light-emitting element for emitting from a firstlight-emitting spot thereof, a first optical signal, and a secondmounting section arranged alongside the first mounting section andhaving a second light-emitting element for emitting from a secondlight-emitting spot thereof, a second optical signal whose wavelength isdifferent from that of the first optical signal; a secondlight-emitting-element pair which is formed of a third mounting sectionhaving a third light-emitting element for emitting from a thirdlight-emitting spot thereof, a third optical signal whose wavelength isdifferent to those of the first and second optical signals, and a fourthmounting section arranged alongside the third mounting section andhaving a fourth light-emitting element for emitting from a fourthlight-emitting spot thereof, a fourth optical signal whose wavelength isdifferent from those of the first to third optical signals; a firstcollimating lens for transforming the first optical signal emitted fromthe first light-emitting spot, into parallel light; a second collimatinglens for transforming the second optical signal emitted from the secondlight-emitting spot, into parallel light; a third collimating lens fortransforming the third optical signal emitted from the thirdlight-emitting spot, into parallel light; a fourth collimating lens fortransforming the fourth optical signal emitted from the fourthlight-emitting spot, into parallel light; an optical multiplex sectionhaving a first filter for transmitting therethrough only the wavelengthof the first optical signal transformed into parallel light by the firstcollimating lens; a front-side mirror for reflecting the first opticalsignal transmitted through the first filter; a second filter arrangedalongside the first filter, for transmitting therethrough only thewavelength of the second optical signal transformed into parallel lightby the second collimating lens, and for reflecting the first opticalsignal reflected by the front-side mirror and multiplexing it with thetransmitted second optical signal; a back-side mirror for reflectingagain the first and second optical signals reflected by the front-sidemirror, toward the front-side mirror; a third filter for transmittingtherethrough only the wavelength of the third optical signal transformedinto parallel light by the third collimating lens; and a fourth filterarranged alongside the third filter, for transmitting therethrough onlythe wavelength of the fourth optical signal transformed into parallellight by the fourth collimating lens, and for reflecting the thirdoptical signal reflected by the front-side mirror and multiplexing itwith the transmitted fourth optical signal; wherein, assuming that adistance between the first light-emitting spot in the first mountingsection and the second light-emitting spot in the second mountingsection and a distance between the third light-emitting spot in thethird mounting section and the fourth light-emitting spot in the fourthmounting section, are each d, a distance between the secondlight-emitting spot in the second mounting section and the thirdlight-emitting spot in the third mounting section is nd (n denotes aninteger of 2 or more); wherein the first light-emitting element ismounted in the first mounting section so as to be displaced from itscenter in a width direction across an emission direction of the firstoptical signal, toward the second light-emitting element; and the secondlight-emitting element is mounted in the second mounting section so asto be displaced from its center in a width direction across an emissiondirection of the second optical signal, toward the first light-emittingelement; and wherein the third light-emitting element is mounted in thethird mounting section so as to be displaced from its center in a widthdirection across an emission direction of the third optical signal,toward the fourth light-emitting element; and the fourth light-emittingelement is mounted in the fourth mounting section so as to be displacedfrom its center in a width direction across an emission direction of thefourth optical signal, toward the third light-emitting element.
 9. Theintegrated optical module of claim 8, wherein the first light-emittingspot is implemented in the first light-emitting element so as to bedisplaced from its center in a width direction across the emissiondirection of the first optical signal, toward the second light-emittingspot; and the second light-emitting spot is implemented in the secondlight-emitting element so as to be displaced from its center in a widthdirection across the emission direction of the second optical signal,toward the first light-emitting spot; and wherein the thirdlight-emitting spot is implemented in the third light-emitting elementso as to be displaced from its center in a width direction across theemission direction of the third optical signal, toward the fourthlight-emitting spot; and the fourth light-emitting spot is implementedin the fourth light-emitting element so as to be displaced from itscenter in a width direction across the emission direction of the fourthoptical signal, toward the third light-emitting spot.
 10. The integratedoptical module of claim 8, wherein the first mounting section and thesecond mounting section are each formed of a mounting board, on bothsurfaces of which an installation region for the first light-emittingelement and an installation region for the second light-emitting elementare respectively and symmetrically provided; and wherein the thirdmounting section and the fourth mounting section are each formed of amounting board, on both surfaces of which an installation region for thethird light-emitting element and an installation region for the fourthlight-emitting element are respectively and symmetrically provided. 11.The integrated optical module of claim 8, wherein the first mountingsection and the second mounting section as well as the third mountingsection and the fourth mounting section, are integrated with each otherso that the first light-emitting spot and the second light-emitting spotas well as the third light-emitting spot and the fourth light-emittingspot, are implemented side by side.
 12. The integrated optical module ofclaim 8, wherein the front-side mirror and the back-side mirror arecomposed of dielectric multi-layer films that are vapor-depositeddirectly on a glass-made holder in its respective locations where thefront-side mirror and the back-side mirror are to be provided.
 13. Theintegrated optical module of claim 8, wherein the back-side mirror isestablished in such a manner that the second filter or the third filteralso covers a location where the back-side mirror is to be provided, tothereby cause reflection.
 14. The integrated optical module of claim 12,wherein the back-side mirror is established in such a manner that thesecond filter or the third filter also covers a location where theback-side mirror is to be provided, to thereby cause reflection.